Semicondutor device with copper plugs having different resistance values

ABSTRACT

Performance of a semiconductor device is improved. In one embodiment, for example, deposition time is increased from 4.6 sec to 6.9 sec. In other words, in one embodiment, thickness of a tantalum nitride film is increased by increasing the deposition time. Specifically, in one embodiment, deposition time is increased such that a tantalum nitride film provided on the bottom of a connection hole to be coupled to a wide interconnection has a thickness within a range from 5 to 10 nm.

CROSS-REFERENCE TO RELATED APPLICATIONS

The disclosure of Japanese Patent Application No. 2014-016841 filed onJan. 31, 2014 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to a semiconductor device and a techniquefor manufacturing the semiconductor device, for example, relates to atechnology that is effectively applied to a semiconductor deviceincluding a copper interconnection and a technique for manufacturing thesemiconductor device.

International Publication WO 2006/016678 describes a semiconductordevice in which a first copper interconnection and a second copperinterconnection having different line widths are provided in the sameinterconnection layer.

SUMMARY

For example, a semiconductor device may include a copper interconnectionincluding copper as a main component, in which a wide interconnection(first copper interconnection) and a narrow interconnection (secondcopper interconnection) having different line widths may be provided inthe same interconnection layer. Specifically, for example, the wideinterconnection is used as a power line for supplying power supplypotential, and the narrow interconnection is used as a signal line fortransmitting a signal.

The wide interconnection and the narrow interconnection are formed inthe same interconnection layer in one step by “damascene process”, forexample. For example, the narrow interconnection is a fineinterconnection formed in minimum working size, and a barrier conductorfilm included in the narrow interconnection is necessary to have a smallthickness in order to secure filling properties of a film in thedamascene process. Hence, since the wide interconnection formed in thesame layer as the narrow interconnection is formed in the same step asthe narrow interconnection, a barrier conductor film included in thewide interconnection necessarily has a small thickness.

For example, when attention is focused on “dual damascene process” inwhich a copper interconnection and a plug are formed together, a barrierconductor film is formed on the bottom of the plug formed together withthe copper interconnection. Consequently, when the barrier conductorfilm is formed to have a small thickness on ground of the fillingproperties of the narrow interconnection formed in minimum working size,a barrier conductor film formed on the bottom of a plug, which isarranged in an underlayer of the narrow interconnection and to becoupled to the narrow interconnection, also has a small thickness, and abarrier conductor film formed on the bottom of a plug, which is arrangedin an underlayer of the wide interconnection and to be coupled to thewide interconnection, also has a small thickness.

In this configuration, a barrier conductor film is interposed betweenthe plug and the lower interconnection. As a result of investigation bythe inventors, it is found that the resistance value of the plugincreases with increase in thickness of the barrier conductor film.Since the wide interconnection must allow high current to passtherethrough, the plug, which is arranged in an underlayer of the wideinterconnection and to be coupled to the wide interconnection, desirablyhas a lower resistance value. Thus, it is desirable to lower theresistance value of the plug that is arranged in an underlayer of thewide interconnection and to be coupled to the wide interconnection. Fromsuch a viewpoint, there is a room for improvement in a currentsemiconductor device and in a current technique for manufacturing thesemiconductor device. In other words, from the viewpoint of improvingperformance of the semiconductor device, there is a room for improvementin the current semiconductor device and in the current technique formanufacturing the semiconductor device.

Other issues and novel features will be clarified from the descriptionof this specification and the accompanying drawings.

According to an embodiment of the present invention, there is provided asemiconductor device that includes a wide interconnection (first copperinterconnection) and a narrow interconnection (second copperinterconnection) provided in the same layer, in which a resistance valueof a first plug (first copper plug) that is arranged in an underlayer ofthe wide interconnection and to be coupled to the wide interconnectionis lower than a resistance value of a second plug (second copper plug)that is arranged in an underlayer of the narrow interconnection and tobe coupled to the narrow interconnection.

According to another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, the methodincluding a step of depositing a tantalum nitride film by a sputteringprocess with tantalum as a target and with nitrogen gas introduced intoa processing chamber, in which deposition time in the deposition step iswithin a range in which the tantalum nitride film formed on the bottomof a first plug (first copper plug) has a thickness of 5 to 10 nm.

According to another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, the methodincluding a step of, after exhausting nitrogen gas, forming a tantalumfilm on a tantalum nitride film by a sputtering process with tantalum asa target and with a substrate draw bias being applied to thesemiconductor substrate, in which the substrate draw bias is appliedsuch that an electric potential on the semiconductor substrate is withina range from −350 to −800 V.

According to the above-described respective embodiments, performance ofthe semiconductor device can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section diagram illustrating an exemplary device structureof a semiconductor device.

FIG. 2 is a section diagram schematically illustrating an exemplaryconfiguration of a multilayer interconnection structure in a partiallyenlarged manner.

FIG. 3 is a section diagram schematically illustrating an exemplaryconfiguration of a multilayer interconnection structure having a fineinterconnection with a half pitch of, for example, about 60 nm or 45 nmin a partially enlarged manner.

FIG. 4 is a graph illustrating a relationship between specificresistance (resistivity) of a stacked film of a tantalum nitride filmand a tantalum film formed thereon, and thickness of the tantalumnitride film.

FIG. 5 is a section diagram illustrating the multilayer interconnectionstructure illustrated in FIG. 1 in a partially enlarged manner.

FIG. 6 is a diagram for qualitatively explaining a difference betweenthickness of a barrier conductor film provided on the bottom of a plugto be coupled to a wide interconnection, and a barrier conductor filmprovided on the bottom of a plug to be coupled to a narrowinterconnection.

FIG. 7 includes graphs illustrating measurement results of plugresistance of a plug to be coupled to a wide interconnection and plugresistance of a plug to be coupled to a narrow interconnection in therelated art.

FIG. 8 is a section diagram illustrating a multilayer interconnectionstructure of an embodiment in a partially enlarged manner.

FIG. 9 includes graphs illustrating measurement results of plugresistance of a plug to be coupled to a wide interconnection and plugresistance of a plug to be coupled to a narrow interconnection in theembodiment.

FIG. 10 is a section diagram illustrating a manufacturing step of asemiconductor device in the embodiment.

FIG. 11 is a section diagram illustrating a manufacturing step of thesemiconductor device following FIG. 10.

FIG. 12 is a section diagram illustrating a manufacturing step of thesemiconductor device following FIG. 11.

FIG. 13 is a section diagram illustrating a manufacturing step of thesemiconductor device following FIG. 12.

FIG. 14 is a section diagram illustrating a manufacturing step of thesemiconductor device following FIG. 13.

FIG. 15 is a section diagram illustrating a manufacturing step of thesemiconductor device following FIG. 14.

FIG. 16 is a diagram illustrating a configuration of a sputteringapparatus used in the embodiment.

FIG. 17 is a table showing a deposition condition in a deposition stepof a tantalum nitride film.

FIG. 18 is a table showing a deposition condition in a deposition stepof a tantalum film.

FIG. 19 is a diagram for explaining introduction timing of nitrogen gasin a deposition step of a tantalum nitride film in a modification.

DETAILED DESCRIPTION

Although the following embodiment may be dividedly described in aplurality of sections or embodiments for convenience as necessary, theyare not unrelated to one another except for the particularly definedcase, and are in a relationship where one is a modification, a detail,supplementary explanation, or the like of part or all of another one.

In the following embodiment, when the number of elements and the like(including the number, a numerical value, amount, a range, etc.) arementioned, the number is not limited to a specified number except forthe particularly defined case and for the case where the number isprincipally clearly limited to the specified number. In other words, thenumber may be not less than or not more than the specified number.

In the following embodiment, it will be appreciated that aconstitutional element (including an element step etc.) of theembodiment are not necessarily indispensable except for the particularlydefined case and for the case where the constitutional element isconsidered to be principally clearly indispensable.

Similarly, in the following embodiment, description on a shape of aconstitutional element or the like, a positional relationship, etc., isintended to include an element having a shape or the like substantiallysimilar to that of the constitutional element except for theparticularly defined case and for the case where such an element isconsidered to be principally clearly not included. The same holds truein each of the numerical value and the range.

In all drawings for explaining the following embodiment, the samecomponents are in principle designated by the same numeral, andduplicated description is omitted. A plan diagram may also be hatchedfor better viewability.

First Embodiment

<Device Structure of Semiconductor Device>

An exemplary device structure of a semiconductor device is nowdescribed. FIG. 1 is a section diagram illustrating an exemplary devicestructure of a semiconductor device. In FIG. 1, for example, MISFETQ isprovided on a semiconductor substrate 1S comprised of silicon singlecrystal. For example, the MISFETQ has a gate insulating film comprisedof a silicon oxide film on a main surface of the semiconductor substrate1S, and has, on the gate insulating film, a gate electrode comprised ofa stacked film of a polysilicon film and a silicide film (such as anickel silicide film) provided on the polysilicon film. For example, asidewall comprised of a silicon oxide film is provided on each oflateral walls on two sides of the gate electrode. A source region and adrain region are provided in alignment with the gate electrode in thesemiconductor substrate 1S below the sidewalls. In this way, the MISFETQis provided on the semiconductor substrate 1S.

In addition, as illustrated in FIG. 1, a contact interlayer insulatingfilm CIL is provided on the semiconductor substrate 1S having theMISFETQ thereon. For example, the contact interlayer insulating film CILis comprised of a stacked film of an ozone TEOS film formed by a thermalCVD process using ozone and tetra ethyl ortho silicate (TEOS) asmaterials, and a plasma TEOS film formed on the ozone TEOS film by aplasma CVD process using TEOS as a material. A plug PLG0 is providedwhile penetrating through the contact interlayer insulating film CIL upto the source or drain region of the MISFETQ. For example, the plug PLG0is formed by filling a contact hole with a barrier conductor filmcomprised of a titanium/titanium nitride film (hereinafter, thetitanium/titanium nitride film refers to a film comprised of titaniumand titanium nitride provided on the titanium), and with a tungsten filmprovided on the barrier conductor film. The titanium/titanium nitridefilm is provided to prevent diffusion of tungsten configuring thetungsten film into silicon, and prevents the contact interlayerinsulating film CIL or the semiconductor substrate 1S from being damagedby fluorine attack thereto during a CVD process in which WF6 (tungstenfluoride) is reduced during formation of the tungsten film. The contactinterlayer insulating film CIL may be comprised of one of a siliconoxide film (SiO₂ film), a SiOF film, and a silicon nitride film.

In addition, an interconnection L1 as a first layer interconnection isprovided on the contact interlayer insulating film CIL. Specifically,the interconnection L1 is provided in an embedded manner in aninterlayer insulating film IL1 provided on the contact interlayerinsulating film CIL having the plug PLC0 therein. Specifically, theinterconnection L1 is formed by filling an interconnection trench, whichpenetrates through the interlayer insulating film IL1 so as to exposethe plug PLG0 at its bottom, with a film including copper as a maincomponent (hereinafter, described as copper film).

In this specification, “main component” refers to a material componentcontained in largest quantities among constitutional materials of anelement (a layer or film). For example, “film including copper as a maincomponent” means that copper (Cu) is contained in largest quantitiesamong constitutional materials of that film. In this specification, forexample, the term “main component” is intentionally used to representthat a conductor film is basically comprised of copper but withoutexcluding the case where the conductor film further contains impurities.

For example, the interlayer insulating film IL1 is comprised of a SiOCfilm, a hydrogen silsesquioxane (HSQ) film (a silicon oxide film formedby a coating process and having a Si—H bond, or a hydrogen-containingsilsesquioxane film), or a methyl silsesquioxane (MSQ) film (a siliconoxide film formed by a coating process and having a Si—C bond, or acarbon-containing silsesquioxane film). In this specification, aninterconnection layer having the interconnection L1 therein may bereferred to as fine layer.

In addition, a second layer interconnection is provided on theinterlayer insulating film IL1 having the interconnection L1 therein.For example, FIG. 1 illustrates a wide interconnection WL2 and a narrowinterconnection NL2 having different line widths as the second layerinterconnection. Specifically, the second layer interconnectionillustrated in FIG. 1 has the wide interconnection WL2 having a largeline width and the narrow interconnection NL2 having a small line width.In other words, in the semiconductor device, for example, the wideinterconnection WL2 and the narrow interconnection NL2 having differentline widths are provided in the same interconnection layer having thesecond layer interconnection therein. In this configuration, forexample, the wide interconnection WL2 is used as a power line thatallows high current to pass therethrough, while the narrowinterconnection NL2 is used as a signal line that may not allow suchhigh current to pass therethrough. Although description is made hereinon an exemplary case where the second layer interconnection has the wideinterconnection WL2 and the narrow interconnection NL2 having differentline widths, any of other interconnection layers also has a plurality ofinterconnections having different line widths in the same layer.

In this way, the second layer interconnection is provided on theinterlayer insulating film IL1. Specifically, a barrier insulating filmB1F1 (liner film) is provided on the interlayer insulating film IL1having the interconnection L1 therein, and an interlayer insulating filmIL2 is provided on the barrier insulating film B1F1. For example, thebarrier insulating film B1F1 is comprised of one of a stacked film of aSiCN film and a SiCO film provided on the SiCN film, a SiC film, and aSiN film. For example, the interlayer insulating film IL2 is comprisedof one of a SiOC film having vacancies, a HSQ film having vacancies, anda MSQ film having vacancies. Each of the vacancies has a size (diameter)of, for example, about 1 nm. The wide interconnection WL2, the narrowinterconnection NL2, a plug PLG1A, and a plug PLG1B are provided in anembedded manner in the barrier insulating film B1F1 and the interlayerinsulating film IL2. In this configuration, the plug PLG1A and the plugPLG1B are provided with the same size in the same layer. The wideinterconnection WL2, the narrow interconnection NL2, the plug PLG1A, andthe plug PLG1B are each comprised of, for example, a copper film. Theinterconnection layer, in which the second layer interconnectionincluding the wide interconnection WL2 and the narrow interconnectionNL2 is provided, is also referred to as fine layer.

As illustrated in FIG. 1, a third layer interconnection and a fourthlayer interconnection are provided in the same way as the second layerinterconnection. Specifically, a barrier insulating film B1F2 isprovided on the interlayer insulating film IL2, and an interlayerinsulating film IL3 is provided on the barrier insulating film B1F2. Forexample, the barrier insulating film B1F2 is comprised of one of astacked film of a SiCN film and a SiCO film provided on the SiCN film, aSiC film, and a SiN film. For example, the interlayer insulating filmIL3 is comprised of one of a SiOC film having vacancies, a HSQ filmhaving vacancies, and a MSQ film having vacancies. An interconnection L3as the third layer interconnection and a plug PLG2 are provided in anembedded manner in the barrier insulating film B1F2 and the interlayerinsulating film IL3. The interconnection L3 and the plug PLG2 are eachalso comprised of, for example, a copper film.

In addition, a barrier insulating film BIF3 is provided on theinterlayer insulating film IL3, and an interlayer insulating film IL4 isprovided on the barrier insulating film BIF3. For example, the barrierinsulating film B1F3 is comprised of one of a stacked film of a SiCNfilm and a SiCO film provided on the SiCN film, a SiC film, and a SiNfilm. For example, the interlayer insulating film IL4 is comprised ofone of a SiOC film having vacancies, a HSQ film having vacancies, and aMSQ film having vacancies. An interconnection L4 as the fourth layerinterconnection and a plug PLG3 are provided in an embedded manner inthe barrier insulating film B1F3 and the interlayer insulating film IL4.The interconnection L4 and the plug PLG3 are each also comprised of, forexample, a copper film. The interconnection layer having theinterconnection L3 therein and the interconnection layer having theinterconnection L4 therein are each also referred to as fine layer.

In addition, a barrier insulating film BIF4 is provided on theinterlayer insulating film IL4, and an interlayer insulating film IL5 isprovided on the barrier insulating film BIF4. For example, the barrierinsulating film B1F4 is comprised of one of a stacked film of a SiCNfilm and a SiCO film, a SiC film, and a SiN film. For example, theinterlayer insulating film IL5 is comprised of one of a silicon oxidefilm (SiO₂ film), a SiOF film, and a TEOS film. A plug PLG4 and aninterconnection L5 as the fifth layer interconnection are provided in anembedded manner in the barrier insulating film B1F4 and the interlayerinsulating film IL5. The interconnection L5 and the plug PLG4 are eachalso comprised of, for example, a copper film. The interconnection layerhaving the interconnection L5 therein is referred to as global layer.

In addition, a pad PD as a sixth layer interconnection is provided onthe interlayer insulating film IL5. For example, the pad PD is comprisedof a film including aluminum as a main component. Specifically, forexample, the pad PD is comprised of one of an aluminum film, an AlSifilm including silicon-doped aluminum, and an AlSiCu film includingaluminum doped with silicon and copper.

A passivation film PAS is provided on the pad PD, and part of the pad PDis exposed from an opening provided in the passivation film PAS. Thepassivation film PAS has a function of protecting the device againstcontamination of an impurity, and is, for example, comprised of asilicon oxide film and a silicon nitride film provided on the siliconoxide film. An undepicted polyimide film is provided on the passivationfilm PAS. The polyimide film is also opened over a region where the padPD is provided.

For example, the pad PD is coupled to an undepicted wire, and a resin asa sealant seals a region on the polyimide film, the region including aportion on the pad PD coupled to the wire. The device structure of thesemiconductor device illustrated in FIG. 1 is configured in this way.

In the device structure illustrated in FIG. 1, the first to sixthinterconnection layers are provided. For example, the first to fourthinterconnection layers each configure the fine layer, and the fifthinterconnection layer configures the global layer. The term “fine layer”refers to an interconnection layer having a fine interconnection in nearminimum working size. The term “global layer” refers to aninterconnection layer in which an interconnection having a size largerthan that of the fine layer is provided. Although FIG. 1 illustrates anexemplary case where the global layer is provided on the fine layer tosimply describe the multilayer interconnection structure, it is in factnormal that “semi-global layer” is provided on the fine layer, and theglobal layer is provided on the semi-global layer. The term “semi-globallayer” refers to an interconnection layer having a size larger than thatof the fine layer but smaller than that of the global layer. In otherwords, when attention is focused on interconnection size, thesemi-global layer is an interconnection layer having an interconnectionhaving a size intermediate between the fine layer and the global layer.

<Room for Improvement>

A schematic device structure of the semiconductor device has beendescribed with reference to FIG. 1. For example, when attention isfocused on an actual copper interconnection, the copper interconnectionis comprised of a barrier conductor film and a copper film. In order toreduce size of a semiconductor device and increase integration thereof,it is necessary for a copper interconnection to be finer. As a result ofinvestigation by the inventors, however, it has been found that a finercopper interconnection causes a difficulty in barrier conductor filmincluded in the copper interconnection, leading to a room forimprovement in terms of improvement in performance of the semiconductordevice. In other words, when attention is focused on the barrierconductor film included in the copper interconnection, the currentsemiconductor device has a room for improvement in terms of improvementin performance of the semiconductor device. Specifically, asemiconductor device including a copper interconnection and a copperplug formed by the damascene process has a room for improvement in termsof lowering a resistance value of the copper plug that is arranged in anunderlayer of the copper interconnection and to be coupled to the copperinterconnection. Such a room for improvement is now described withreference to drawings.

FIG. 2 is a section diagram schematically illustrating an exemplaryconfiguration of a multilayer interconnection structure in a partiallyenlarged manner. As illustrated in FIG. 2, for example, a plug PLG andan interconnection L2, which each include copper as a main component andare integrally formed by “dual damascene process”, are arranged on theinterconnection L1 that includes copper as a main component and isformed by “single damascene process”. That is, the interconnection L1 asa lower interconnection is electrically coupled to the interconnectionL2 as an upper interconnection via the plug PLG. The plug PLG is formedby filling a connection hole CNT with a barrier conductor film BCF and acopper film, and the interconnection L2 is formed by filling aninterconnection trench WD integrally formed with the connection hole CNTwith the barrier conductor film BCF and the copper film CF. For example,the barrier conductor film BCF is comprised of a tantalum nitride filmTNF provided on each of inner walls of the connection hole CNT and theinterconnection trench WD, and a tantalum film TF provided on thetantalum nitride film TNF.

In this way, the barrier conductor film BCF is provided on each of theinner walls of the connection hole CNT and the interconnection trench WDinstead of directly providing the copper film thereon. This is toprevent diffusion of copper configuring the copper film into siliconconfiguring the semiconductor substrate due to heat treatment or thelike. Specifically, since the diffusion constant of a copper atom intosilicon is relatively large, copper easily diffuses into silicon. Asemiconductor element such as MISFET is provided in the semiconductorsubstrate. Diffusion of copper atoms into a formation region of thesemiconductor element causes degradation in properties of thesemiconductor element typified by insufficient withstanding voltage.Consequently, the barrier conductor film BCF is provided to preventcopper atoms from being diffused from the copper film configuring theinterconnection. In other words, the barrier conductor film BCF has afunction of preventing diffusion of copper atoms. In this way, forexample, as illustrated in FIG. 2, the actual multilayer interconnectionis designed such that the plug PLG and the interconnection L2, which areintegrally formed and each include copper as a main component, arearranged on the interconnection L1 including copper as a main component.

In FIG. 2, it is assumed that line width of the interconnection L2 islarge compared with the minimum working size. In this case, even if thethickness of the barrier conductor film BCF is increased, degradation infilling properties is less likely to be a significant problem when theinterconnection trench WD is filled with the copper film CF. Hence, thebarrier conductor film BCF having a large thickness is provided on eachof the inner walls of the connection hole CNT and the interconnectiontrench WD.

However, in the case where a fine interconnection with a half pitch of,for example, about 60 nm or 45 nm is formed, a different situationoccurs. FIG. 3 is a section diagram schematically illustrating anexemplary configuration of a multilayer interconnection structure havinga fine interconnection with a half pitch of, for example, about 60 nm or45 nm in a partially enlarged manner. In FIG. 3, the plug PLG and theinterconnection L2, which are integrally formed by the dual damasceneprocess and each include copper as a main component, are also arrangedon the interconnection L1 that is formed by the single damascene processand includes copper as a main component. In this configuration, when theinterconnection L2 is a fine interconnection, and if the thickness ofthe barrier conductor film BCF is increased, degradation in fillingproperties becomes a significant problem when the interconnection trenchWD is filled with the copper film CF. Hence, the barrier conductor filmBCF on each of the inner walls of the connection hole CNT and theinterconnection trench WD is necessary to have a thickness smaller thanthat of the barrier conductor film BCF illustrated in FIG. 2.

Comparing FIG. 2 with FIG. 3, therefore, even if size of the plug PLGillustrated in FIG. 2 is equal to size of the plug PLG illustrated inFIG. 3, the thickness of the barrier conductor film BCF provided on thebottom of the plug PLG illustrated in FIG. 3 is smaller than thethickness of the barrier conductor film BCF provided on the bottom ofthe plug PLG illustrated in FIG. 2. Consequently, plug resistance (viaresistance) of the plug PLG illustrated in FIG. 2 is different from plugresistance of the plug PLG illustrated in FIG. 3.

Specifically, resistivity (specific resistance) of the barrier conductorfilm BCF is higher than resistivity of the copper film CF. Consequently,when current is applied from the interconnection L2 to theinterconnection L1 via the plug PLG (see an arrow in each of FIGS. 2 and3), it is likely that plug resistance of the plug PLG with the thickbarrier conductor film BCF illustrated in FIG. 2 is higher than plugresistance of the plug PLG with the thin barrier conductor film BCFillustrated in FIG. 3. Actually, however, plug resistance of the plugPLG with the thick barrier conductor film BCF illustrated in FIG. 2 ishigher than plug resistance of the plug PLG with the thin barrierconductor film BCF illustrated in FIG. 3. In other words, plugresistance of the plug PLG with the thin barrier conductor film BCFillustrated in FIG. 3 is higher than plug resistance of the plug PLGwith the thick barrier conductor film BCF illustrated in FIG. 2.Specifically, as illustrated in FIG. 3, when the interconnection L2 iscomprised of a fine interconnection with a half pitch of, for example,about 60 nm or 45 nm, plug resistance of the plug PLG, which is arrangedin an underlayer of the interconnection L2 and to be coupled to theinterconnection L2, increases.

Thus, plug resistance of the plug PLG with the thin barrier conductorfilm BCF illustrated in FIG. 3 is higher than plug resistance of theplug PLG with the thick barrier conductor film BCF illustrated in FIG.2. One reason for this is now described.

In FIG. 2, the barrier conductor film BCF having a large thickness isprovided on the bottom of the plug PLG. In this case, the barrierconductor film BCF is comprised of the tantalum nitride film TNF and thetantalum film TF provided on the tantalum nitride film TNF; hence, itcan be considered that the tantalum nitride film TNF also has asufficiently large thickness. When the tantalum nitride film TNF has asufficiently large thickness in this way, the tantalum film TF providedon the tantalum nitride film TNF has a crystal structure of a α-Tastructure being a body-centered structure.

On the other hand, in FIG. 3, the barrier conductor film BCF having asmall thickness is provided on the bottom of the plug PLG. Hence, it canbe considered that the tantalum nitride film TNF as a constitutionalfilm of the barrier conductor film BCF also has a small thickness. Whenthe tantalum nitride film TNF has a small thickness in this way, thetantalum film TF provided on the tantalum nitride film TNF has a crystalstructure of a β-Ta structure being a tetragonal structure.

That is, while the crystal structure of tantalum is the α-Ta structurein the case of the plug PLG with the thick barrier conductor film BCFillustrated in FIG. 2, the crystal structure of tantalum is the β-Tastructure in the case of the plug PLG with the thin barrier conductorfilm BCF illustrated in FIG. 3. This causes the plug resistance of theplug PLG illustrated in FIG. 3 to be higher than the plug resistance ofthe plug PLG illustrated in FIG. 2. This is because resistivity of theα-Ta structure is lower than resistivity of the β-Ta structure.Specifically, the entire plug PLG with the thick barrier conductor filmBCF illustrated in FIG. 2 has a low plug resistance. This is becausealthough the barrier conductor film BCF has a large thickness, thetantalum film configuring the barrier conductor film BCF has a crystalstructure of the α-Ta structure having low resistivity. On the otherhand, the entire plug PLG with the thin barrier conductor film BCFillustrated in FIG. 3 has a high plug resistance. This is becausealthough the barrier conductor film BCF has a small thickness, thetantalum film configuring the barrier conductor film BCF has a crystalstructure of the β-Ta structure having high resistivity.

Thus, when attention is focused only on the thickness itself of thebarrier conductor film BCF, it is likely that the plug resistance of theplug PLG illustrated in FIG. 2 is higher than the plug resistance of theplug PLG illustrated in FIG. 3. Actually, however, considering that thetantalum film has different crystal structures between the plug PLGillustrated in FIG. 2 and the plug PLG illustrated in FIG. 3, the plugresistance of the plug PLG illustrated in FIG. 2 is lower than the plugresistance of the plug PLG illustrated in FIG. 3. Specifically, when thetantalum nitride film has a large thickness, the tantalum film providedon the tantalum nitride film has a crystal structure of the α-Tastructure having low resistivity. Hence, in terms of lowering the plugresistance of the plug PLG, the thickness of the tantalum nitride filmprovided under the tantalum film is desirably increased to the extentthat the tantalum film has a crystal structure of the α-Ta structure.

FIG. 4 is a graph illustrating a relationship between specificresistance (resistivity) of a stacked film of the tantalum nitride filmand the tantalum film formed thereon, and thickness of the tantalumnitride film. In FIG. 4, a horizontal axis shows thickness (TaNthickness) of the tantalum nitride film, and a vertical axis showsspecific resistance of the stacked film. In this case, the stacked filmof the tantalum nitride film and the tantalum film provided thereon isprepared, and thickness of the tantalum nitride film is varied whilethickness of the tantalum film (Ta thickness) is fixed. The graph ofFIG. 4 shows a measurement results of the specific resistance of thestacked film in such a case. As illustrated in FIG. 4, increasing thethickness of the tantalum nitride film decreases the specific resistanceof the stacked film of the tantalum nitride film and the tantalum filmprovided thereon. Specifically, when the thickness of the tantalumnitride film is about 3 nm, the specific resistance of the stacked filmis about 210 μΩ·cm. When the thickness of the tantalum nitride film isabout 5 nm, the specific resistance of the stacked film is about 150μΩ·cm. When the thickness of the tantalum nitride film is about 6 nm,the specific resistance of the stacked film is about 90 μΩ·cm. When thethickness of the tantalum nitride film is about 7 nm, the specificresistance of the stacked film decreases to about 70 μΩ·cm. Inparticular, the specific resistance of the stacked film remarkablyvaries at a thickness of the tantalum nitride film of about 5 nm ormore. It is therefore likely that when the tantalum nitride film has athickness of, for example, 5 nm or more, the tantalum film provided onthe tantalum nitride film has a crystal structure of the α-Ta structure,leading to low specific resistance of the stacked film. In other words,when the tantalum nitride film has a thickness of, for example, lessthan 5 nm, the tantalum film provided on the tantalum nitride film has acrystal structure of the β-Ta structure, leading to high specificresistance of the stacked film. Hence, the results shown in FIG. 4possibly back up that the thickness of the tantalum nitride filmprovided under the tantalum film is desirably increased to the extentthat the tantalum film has a crystal structure of the α-Ta structure interms of decreasing the plug resistance of the plug PLG.

In this way, the thickness of the tantalum nitride film provided underthe tantalum film is desirably increased in terms of decreasing the plugresistance of the plug PLG. As described above, however, when theinterconnection L2 is a fine interconnection (with a half pitch of about60 nm or 45 nm), and if the thickness of the barrier conductor film BCFis increased, it is a significant problem that filling properties aredegraded when the interconnection trench WD is filled with the copperfilm CF. Consequently, the interconnection L2 as a fine interconnectionillustrated in FIG. 3 is necessary to be designed such that the barrierconductor film BCF provided on each of the inner walls of the connectionhole CNT and the interconnection trench WD has a small thickness interms of improving the filling properties. In this case, however, asillustrated in FIG. 3, the tantalum nitride film provided on the bottomof the plug PLG has a small thickness, and thus the tantalum filmprovided on the tantalum nitride film has a crystal structure of theβ-Ta structure having high resistivity. This results in high plugresistance of the plug PLG to be coupled to the interconnection L2 as afine interconnection illustrated in FIG. 3.

However, such high plug resistance is actually a significant problem,for example, in the plug PLG1A to be electrically coupled to the wideinterconnection WL2 provided in the same layer as the narrowinterconnection NL2 illustrated in FIG. 1. Specifically, when attentionis focused on the wide interconnection WL2 and the narrowinterconnection NL2 provided in the same layer as illustrated in FIG. 1,the above-described problem is significant in the plug PLG1Aelectrically coupled to the wide interconnection WL2 having a large linewidth and provided in the same layer as the narrow interconnection NL2rather than the plug PLG1B electrically coupled to the narrowinterconnection NL2 having a small line width. In this regard,description is made below.

FIG. 5 is a section diagram illustrating the multilayer interconnectionstructure illustrated in FIG. 1 in a partially enlarged manner. In FIG.5, for example, the barrier insulating film B1F1 is provided on theinterlayer insulating film IL1 having therein the interconnection L1 asthe first interconnection, and the interlayer insulating film IL2 isprovided on the barrier insulating film B1F1. The interconnection trenchWD2A and the connection hole CNT1A are integrally provided in thebarrier insulating film B1F1 and the interlayer insulating film IL2 soas to penetrate through the barrier insulating film B1F1 and theinterlayer insulating film IL2. Similarly, the interconnection trenchWD2B and the connection hole CNT1B are integrally provided in thebarrier insulating film B1F1 and the interlayer insulating film IL2 soas to penetrate through the barrier insulating film B1F1 and theinterlayer insulating film IL2.

The barrier conductor film BCF is provided on each of the inner walls ofthe interconnection trench WD2A and the connection hole CNT1A, and thecopper film CF is provided on the barrier conductor film BCF so as tofill the interconnection trench WD2A and the connection hole CNT1A.Thus, there is provided the plug PLG1A including the barrier conductorfilm BCF and the copper film CF filling the connection hole CNT1A, andprovided the wide interconnection WL2 including the barrier conductorfilm BCF and the copper film CF filling the interconnection trench WD2A.

Similarly, the barrier conductor film BCF is provided on each of theinner walls of the interconnection trench WD2B and the connection holeCNT1B, and the copper film CF is provided on the barrier conductor filmBCF so as to fill the interconnection trench WD2B and the connectionhole CNT1B. Thus, there is provided the plug PLG1B including the barrierconductor film BCF and the copper film CF filling the connection holeCNT1B, and provided the narrow interconnection NL2 including the barrierconductor film BCF and the copper film CF filling the interconnectiontrench WD2B.

In this way, the wide interconnection WL2 and the narrow interconnectionNL2 are provided in the same layer, and the plug PLG1A and the plugPLG1B are provided in the same layer. That is, as illustrated in FIG. 5,the wide interconnection WL2 and the narrow interconnection NL2 havingdifferent line widths are provided in the same layer. The wideinterconnection WL2 and the narrow interconnection NL2 are formed in thesame layer in one step by the damascene process, for example. Forexample, the narrow interconnection NL2 is a fine interconnection formedin minimum working size, and the barrier conductor film BCF provided inthe narrow interconnection NL2 is necessary to be small in thickness inorder to secure filling properties of a film in the damascene process.Hence, the wide interconnection WL2 provided in the same layer as thenarrow interconnection NL2 necessarily has the barrier conductor filmBCF having a small thickness since the wide interconnection WL2 isformed in the same step as that for the narrow interconnection NL2.Consequently, the tantalum nitride film TNF, which is provided on thebottom of the plug PLG1A to be coupled to the wide interconnection WL2,has a small thickness, and thus the tantalum film TF provided on thetantalum nitride film TNF has a crystal structure of the β-Ta structurehaving high resistivity. This results in high plug resistance of theplug PLG1A to be coupled to the wide interconnection WL2. Naturally, thetantalum nitride film TNF, which is provided on the bottom of the plugPLG1B to be coupled to the narrow interconnection NL2, also has a smallthickness, and thus the tantalum film TF provided on the tantalumnitride film TNF has a crystal structure of the β-Ta structure havinghigh resistivity. As a result, the plug PLG1B to be coupled to thenarrow interconnection NL2 also has high plug resistance.

In this way, since the wide interconnection WL2 and the narrowinterconnection NL2 are formed in the same layer in one step (by thedual damascene process), the thickness of the barrier conductor film BCFis limited in terms of the filling properties of the narrowinterconnection NL2. Hence, the plug PLG1A to be coupled to the wideinterconnection WL2 and the plug PLG1B to be coupled to the narrowinterconnection NL2 are each increased in plug resistance. In this case,increase in plug resistance of the plug PLG1A to be coupled to the wideinterconnection WL2 is a particularly significant problem causingdegradation in performance of the semiconductor device. Some reasons forthis are now described.

A first reason is that the wide interconnection WL2 is used as a powerline for supplying power potential, for example. Specifically, the wideinterconnection WL2 is used as a power line that allows high current topass therethrough, and is therefore required to have low interconnectionresistance. Hence, the plug PLG1A to be electrically coupled to the wideinterconnection WL2 is also required to have low plug resistance. Thisis because if the plug PLG1A to be electrically coupled to the wideinterconnection WL2 has high plug resistance, and when a high current isapplied to the wide interconnection WL2, voltage drop in the plug PLG1Aincreases, so that significant voltage drop from the power voltageoccurs.

On the other hand, in the case of the plug PLG1B to be electricallycoupled to the narrow interconnection NL2, even if plug resistancesomewhat increases, such an increase is not a significant problem. Thisis because the narrow interconnection NL2 is used as, for example, asignal line for transmitting a signal, and may not allow a current ashigh as the current for the power line to pass therethrough.Specifically, it is likely that the narrow interconnection NL2 is lessaffected by the plug resistance compared with the wide interconnectionWL2 due to a difference in function between the narrow interconnectionNL2 and the wide interconnection WL2. Consequently, increase in plugresistance is particularly serious in the plug PLG1A to be coupled tothe wide interconnection WL2 in terms of suppressing degradation inperformance of the semiconductor device.

A second reason is now described. As illustrated in FIG. 5, thethickness of the barrier conductor film BCF on the bottom of the plugPLG1A to be coupled to the wide interconnection WL2 is larger than thethickness of the barrier conductor film BCF on the bottom of the plugPLG1B to be coupled to the narrow interconnection NL2. In other words,even if such barrier conductor films BCF are formed in one step, thethickness of the barrier conductor film BCF on the bottom of the plugPLG1A is larger than the thickness of the barrier conductor film BCF onthe bottom of the plug PLG1B.

For example, this phenomenon can be qualitatively considered as follows.For example, the barrier conductor film BCF is formed by a sputteringprocess. In the sputtering process, for example, argon is allowed tocollide with a target comprised of a deposition material to emit targetatoms that then adhere onto the semiconductor substrate, and therebydeposition is performed. It is assumed that a barrier conductor film isformed on each of the bottoms of the connection hole CNT1A and theconnection hole CNT1B by a one-step sputtering process, as illustratedin FIG. 6. In this case, a target atom adhering onto the bottom of theconnection hole CNT1A possibly comes from a direction within a rangedefined by an angle θ1 illustrated in FIG. 6. On the other hand, atarget atom adhering onto the bottom of the connection hole CNT1Bpossibly comes from a direction within a range defined by an angle θ2illustrated in FIG. 6. Considering that width of the interconnectiontrench WD2A provided on the connection hole CNT1A is larger than widthof the interconnection trench WD2B provided on the connection hole CNT1Bas illustrated in FIG. 6, the angle θ1 is larger than the angle θ2. Thismeans that the number of target atoms adhering onto the bottom of theconnection hole CNT 1A is larger than the number of target atomsadhering onto the bottom of the connection hole CNT 1B. As a result,thickness of the barrier conductor film provided on the bottom of theconnection hole CNT 1A is larger than thickness of the barrier conductorfilm provided on the bottom of the connection hole CNT 1B. Consequently,as illustrated in FIG. 5, thickness of the barrier conductor film BCFprovided on the bottom of the plug PLG1A is larger than thickness of thebarrier conductor film BCF provided on the bottom of the plug PLG1B.

Thus, since the barrier conductor film BCF provided on the bottom of theplug PLG1B to be coupled to the narrow interconnection NL2 has a smallthickness, the tantalum film TF provided on the bottom of the plug PLG1Bto be coupled to the narrow interconnection NL2 has a crystal structureof the β-Ta structure having high resistivity. On the other hand, whilethe barrier conductor film BCF provided on the bottom of the plug PLG1Ato be coupled to the wide interconnection WL2 is formed to have athickness larger than the thickness of the barrier conductor film BCFprovided on the bottom of the plug PLG1B, the thickness of the formedtantalum nitride film TNF is still not large enough for the tantalumfilm TF to have a crystal structure of the α-Ta structure. Specifically,even if it is considered that the thickness of the barrier conductorfilm BCF provided on the bottom of the plug PLG1A is larger than thethickness of the barrier conductor film BCF provided on the bottom ofthe plug PLG1B, the tantalum nitride film TNF provided on the bottom ofthe plug PLG1A has a thickness of less than 5 nm in an existingdeposition condition. Consequently, the tantalum film TF provided on thebottom of the plug PLG1A to be coupled to the wide interconnection WL2is also likely to have a crystal structure of the β-Ta structure havinghigh resistivity.

Hence, the tantalum film TF provided on the bottom of the plug PLG1A andthe tantalum film TF provided on the bottom of the plug PLG1B have thesame crystal structure of the β-Ta structure. Assuming this, when it isconsidered that the thickness of the barrier conductor film BCF providedon the bottom of the plug PLG1A is larger than the thickness of thebarrier conductor film BCF provided on the bottom of the plug PLG1B, theplug resistance of the plug PLG1A to be coupled to the wideinterconnection WL2 must be higher than the plug resistance of the plugPLG1B to be coupled to the narrow interconnection NL2.

FIG. 7 includes graphs illustrating measurement results of the plugresistance of the plug PLG1A to be coupled to the wide interconnectionWL2 and the plug resistance of the plug PLG1B to be coupled to thenarrow interconnection NL2 in the related art. In FIG. 7, a graphdesignated as “Wide” shows the plug resistance of the plug PLG1A to becoupled to the wide interconnection WL2, and a graph designated as“Narrow” shows the plug resistance of the plug PLG1B to be coupled tothe narrow interconnection NL2. As illustrated in FIG. 7, the plugresistance of the plug PLG1A to be coupled to the wide interconnectionWL2 is higher than the plug resistance of the plug PLG1B to be coupledto the narrow interconnection NL2.

In this way, increase in plug resistance of the plug PLG1A to be coupledto the wide interconnection WL2 is a significant problem. Specifically,the wide interconnection WL2 is used as a power line that allows highcurrent to pass therethrough. In addition, the plug resistance of theplug PLG1A to be coupled to the wide interconnection WL2 is higher thanthe plug resistance of the plug PLG1B to be coupled to the narrowinterconnection NL2. Such two events synergistically make the increasein plug resistance of the plug PLG1A, which is to be coupled to the wideinterconnection WL2, to be a significant problem.

In this embodiment, therefore, there is devised a technique forsuppressing the increase in plug resistance of the plug to be coupled tothe wide interconnection in the semiconductor device having the wideinterconnection and the narrow interconnection in the same layer. Thetechnical idea of this embodiment as a basis of the devised technique isnow described.

<Structural Characteristics of Embodiment>

FIG. 8 is a section diagram illustrating a multilayer interconnectionstructure of this embodiment in a partially enlarged manner. In FIG. 8,for example, the barrier insulating film B1F1 is provided on theinterlayer insulating film IL1 having therein the interconnection L1 asthe first interconnection, and the interlayer insulating film IL2 isprovided on the barrier insulating film B1F1. The interconnection trenchWD2A and the connection hole CNT1A are integrally provided in thebarrier insulating film B1F1 and the interlayer insulating film IL2 soas to penetrate through the barrier insulating film B1F1 and theinterlayer insulating film IL2. Similarly, the interconnection trenchWD2B and the connection hole CNT1B are integrally provided in thebarrier insulating film B1F1 and the interlayer insulating film IL2 soas to penetrate through the barrier insulating film B1F1 and theinterlayer insulating film IL2.

The barrier conductor film BCF is provided on each of the inner walls ofthe interconnection trench WD2A and the connection hole CNT1A, and thecopper film CF is provided on the barrier conductor film BCF so as tofill the interconnection trench WD2A and the connection hole CNT1A.Thus, there is provided the plug PLG1A including the barrier conductorfilm BCF and the copper film CF filling the connection hole CNT1A, andprovided the wide interconnection WL2 including the barrier conductorfilm BCF and the copper film CF filling the interconnection trench WD2A.

Similarly, the barrier conductor film BCF is provided on each of theinner walls of the interconnection trench WD2B and the connection holeCNT1B, and the copper film CF is provided on the barrier conductor filmBCF so as to fill the interconnection trench WD2B and the connectionhole CNT1B. Thus, there is provided the plug PLG1B including the barrierconductor film BCF and the copper film CF filling the connection holeCNT1B, and provided the narrow interconnection NL2 including the barrierconductor film BCF and the copper film CF filling the interconnectiontrench WD2B.

In this way, the semiconductor device of this embodiment includes thewide interconnection WL2 and the narrow interconnection NL2 that areprovided in the same layer (the same interconnection layer) and eachinclude copperas a main component, the plug PLG1A including copper as amain component and being arranged in an underlayer of the wideinterconnection WL2 and coupled to the wide interconnection WL2, and theplug PLG1B including copper as a main component and being arranged in anunderlayer of the narrow interconnection NL2 and coupled to the narrowinterconnection NL2. Each of the plug PLG1A and the plug PLG1B includesthe barrier conductor film BCF. In this configuration, while the linewidth of the wide interconnection WL2 is larger than the line width ofthe narrow interconnection NL2, the plug PLG1A and the plug PLG1B areprovided with the same size in the same layer. For example, the barrierconductor film BCF is comprised of the tantalum nitride film TNF and thetantalum film TF provided on the tantalum nitride film TNF.

For example, as illustrated in FIG. 8, this embodiment is characterizedin that the thickness of the barrier conductor film BCF provided on thebottom of the plug PLG1A to be coupled to the wide interconnection WL2is larger than the thickness of the barrier conductor film BCF providedon the bottom of the plug PLG1B to be coupled to the narrowinterconnection NL2. More in detail, the thickness of the tantalumnitride film TNF provided on the bottom of the plug PLG1A is larger thanthe thickness of the tantalum nitride film TNF provided on the bottom ofthe plug PLG1B, and the thickness of the tantalum nitride film TNFprovided on the bottom of the plug PLG1A is large enough for thetantalum film TF provided on the tantalum nitride film TNF to have acrystal structure of the α-Ta structure. Specifically, the tantalumnitride film TNF, which is provided on the bottom of the plug PLG1A andto be coupled to the wide interconnection WL2, has a thickness of 5 to10 nm. On the other hand, the tantalum nitride film TNF, which isprovided on the bottom of the plug PLG1B and to be coupled to the narrowinterconnection NL2, has a thickness of more than 0 nm and 3 nm or less.In this case, the tantalum film TF, which is provided on the tantalumnitride film TNF on the bottom of the plug PLG1A to be coupled to thewide interconnection WL2, has a crystal structure of the α-Ta structurehaving low resistivity. On the other hand, the tantalum film TF, whichis provided on the tantalum nitride film TNF on the bottom of the plugPLG1B to be coupled to the narrow interconnection NL2, has a crystalstructure of the β-Ta structure having high resistivity. In thisembodiment, therefore, the resistivity of the tantalum film TF providedon the bottom of the plug PLG1A is lower than the resistivity of thetantalum film TF provided on the bottom of the plug PLG1B.

Specifically, FIG. 9 includes graphs illustrating measurement results ofthe plug resistance of the plug PLG1A to be coupled to the wideinterconnection WL2 and the plug resistance of the plug PLG1B to becoupled to the narrow interconnection NL2 in this embodiment. In FIG. 9,a graph designated as “Wide” shows the plug resistance of the plug PLG1Ato be coupled to the wide interconnection WL2, and a graph designated as“Narrow” shows the plug resistance of the plug PLG1B to be coupled tothe narrow interconnection NL2. As illustrated in FIG. 9, the plugresistance of the plug PLG1A to be coupled to the wide interconnectionWL2 is lower than the plug resistance of the plug PLG1B to be coupled tothe narrow interconnection NL2.

In this way, according to this embodiment, the resistance value (plugresistance) of the plug PLG1A to be coupled to the wide interconnectionWL2 is allowed to be lower than the resistance value (plug resistance)of the plug PLG1B to be coupled to the narrow interconnection NL2.Hence, according to this embodiment, it is possible to suppress increasein plug resistance of the plug PLG1A to be coupled to the wideinterconnection WL2 used as, for example, a power line, leading toimprovement in performance of the semiconductor device.

In addition, according to this embodiment, it is possible to decreasethe thickness of the barrier conductor film BCF provided on the innerwall of the interconnection trench WD2B; hence, it is possible toimprove the filling properties for forming the narrow interconnectionNL2 with a processing accuracy of about minimum working size.

Consequently, in this embodiment, for example, the following significanteffect can be provided. That is, there is provided the semiconductordevice having in the same layer the wide interconnection WL2 used as apower line that allows high current to pass therethrough and the narrowinterconnection NL2 formed with the processing accuracy of about minimumworking size, in which while the plug resistance of the plug PLG1A to becoupled to the wide interconnection WL2 is decreased, the fillingproperties for forming the narrow interconnection NL2 as a fineinterconnection is improved.

<Method of Manufacturing Semiconductor Device>

The semiconductor device of this embodiment is configured as describedabove. A method of manufacturing the semiconductor device is nowdescribed with reference to drawings. The following manufacturingprocess is exemplarily described with a process in which theinterconnection L1 is formed by the single damascene process in aninterlayer insulating film provided above a semiconductor substrate, andthen a multilayer interconnection structure is formed by the dualdamascene process.

First, as illustrated in FIG. 10, the barrier insulating film B1F1 isformed on the interlayer insulating film IL1 having the interconnectionL1 therein, and the interlayer insulating film IL2 is formed on thebarrier insulating film B1F1. For example, the barrier insulating filmB1F1 is comprised of one of a stacked film of a SiCN film and a SiCOfilm provided on the SiCN film, a SiC film, and a SiN film, and, forexample, can be formed by a chemical vapor deposition (CVD) process. Forexample, the interlayer insulating film IL2 is comprised of alow-dielectric-constant film having a dielectric constant lower thanthat of a silicon oxide film. Specifically, for example, the interlayerinsulating film IL2 can be comprised of a low-dielectric-constant filmsuch as a SiOC film formed by the CVD process, or a HSQ or MSQ filmformed by a coating process.

Subsequently, as illustrated in FIG. 11, the interconnection trench WD2Aintegrated with the connection hole CNT1A and the interconnection trenchWD2B integrated with the connection hole CNT1B are each formed so as topenetrate through the barrier insulating film B1F1 and the interlayerinsulating film IL2 by using a photolithography technique and an etchingtechnique. At this time, a surface of the interconnection L1 formed soas to be embedded in the interlayer insulating film IL1 is exposed ateach of the bottoms of the connection hole CNT 1A and the connectionhole CNT 1B. In this step, as illustrated in FIG. 11, width of theinterconnection trench WD2A is made larger than width of theinterconnection trench WD2B, and size of the connection hole CNT1A andsize of the connection hole CNT1B are made equal to each other. In otherwords, the interconnection trench WD2B is formed with a dimensionaccuracy of, for example, about minimum working size, and theinterconnection trench WD2A is formed with a dimension accuracy rougherthan minimum working size, for example.

Subsequently, as illustrated in FIG. 12, the tantalum nitride film TNFis formed over a region on the interlayer insulating film IL2 by, forexample, a sputtering process, the region including each of the innerwalls of the interconnection trench WD2A and the connection hole CNT1Aand each of the inner walls of the interconnection trench WD2B and theconnection hole CNT1B. At this time, as illustrated in FIG. 12, thethickness of the tantalum nitride film TNF formed on the bottom of theconnection hole CNT1A is larger than the thickness of the tantalumnitride film TNF formed on the bottom of the connection hole CNT1B.Specifically, in this embodiment, a deposition condition in thesputtering process is devised such that the tantalum nitride film TNF isformed to have a thickness of 5 to 10 nm on the bottom of the connectionhole CNT1A, and have a thickness of more than 0 nm and 3 nm or less onthe bottom of the connection hole CNT1B. The deposition condition in thesputtering process for forming the tantalum nitride film TNF isdescribed in detail later (first characteristic point in manufacturing).

Subsequently, as illustrated in FIG. 13, the tantalum film TF is formedon the tantalum nitride film TNF by using, for example, a sputteringprocess. At this time, since the tantalum nitride film TNF has athickness of 5 to 10 nm on the bottom of the connection hole CNT1A, thetantalum film TF formed on such a tantalum nitride film TNF has acrystal structure of the α-Ta structure having low resistivity. On theother hand, since the tantalum nitride film TNF has a thickness of morethan 0 nm and 3 nm or less on the bottom of the connection hole CNT1B,the tantalum film TF formed on such a tantalum nitride film TNF has acrystal structure of the β-Ta structure having high resistivity. In thisembodiment, there is also devised a technique on the depositioncondition in the sputtering process for forming the tantalum film TF.According to the devised technique, in this embodiment, the tantalumfilm TF formed on the tantalum nitride film TNF tends to have a crystalstructure of the α-Ta structure. The deposition condition in thesputtering process for forming the tantalum film TF is described indetail later (second characteristic point in manufacturing)

In this way, the barrier conductor film BCF comprised of the tantalumnitride film TNF and the tantalum film TF can be formed over a region onthe interlayer insulating film IL2, the region including each of theinner walls of the interconnection trench WD2A and the connection holeCNT1A and each of the inner walls of the interconnection trench WD2B andthe connection hole CNT1B.

Subsequently, as illustrated in FIG. 14, a seed film SL comprised of,for example, a thin copper film is formed over a region on the barrierconductor film BCF, the region including each of the insides of theinterconnection trench WD2A and the connection hole CNT1A and each ofthe insides of the interconnection trench WD2B and the connection holeCNT1B. Although the seed film SL can be formed by, for example, asputtering process, this is not limitative, and the seed film SL may beformed by, for example, a CVD process, an atomic layer deposition (ALD)process, or a plating process.

Subsequently, as illustrated in FIG. 15, for example, the copper film CFis formed by an electrolytic plating process with the seed film SL as anelectrode. The copper film CF is formed so as to fill each of theinsides of the interconnection trench WD2A and the connection hole CNT1Aand each of the insides of the interconnection trench WD2B and theconnection hole CNT1B. At this time, in this embodiment, while thebarrier conductor film BCF is formed on each of the inner walls of theinterconnection trench WD2B and the connection hole CNT 1B that areformed with the processing accuracy of about minimum working size, thebarrier conductor film BCF still has a small thickness. It is thereforepossible to improve filling properties when the interconnection trenchWD2B is filled with the copper film CF.

The copper film CF is comprised of, for example, a film including copperas a main component. Specifically, the copper film CF is comprised ofcopper (Cu), or copper alloy (alloy of copper (Cu) and one of aluminum(Al), magnesium (Mg), titanium (Ti), manganese (Mn), iron (Fe), zinc(Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru),palladium (Pd), silver (Ag), gold (Au), indium (In), lanthanoid seriesmetal, actinide series metal, and the like). The copper film CF may beformed not only by the electrolytic plating process but also by asputtering process or a CVD process.

Subsequently, as illustrated in FIG. 8, the unnecessary barrierconductor film BCF and copper film CF formed on the interlayerinsulating film IL2 are removed by a chemical mechanical polishing (CMP)process. On the other hand, the copper film CF and the barrier conductorfilm BCF are left in each of the insides of the interconnection trenchWD2A and the connection hole CNT1A, and in each of the insides of theinterconnection trench WD2B and the connection hole CNT1B. Consequently,according to this embodiment, as illustrated in FIG. 8, it is possibleto form the wide interconnection WL2 including the barrier conductorfilm BCF and the copper film CF filling the interconnection trench WD2A,and form the plug PLG1A including the barrier conductor film BCF and thecopper film CF filling the connection hole CNT1A. Similarly, accordingto this embodiment, it is possible to form the narrow interconnectionNL2 including the barrier conductor film BCF and the copper film CFfilling the interconnection trench WD2B, and form the plug PLG1Bincluding the barrier conductor film BCF and the copper film CF fillingthe connection hole CNT1B. In this way, in this embodiment, the copperfilm CF included in the wide interconnection WL2 (first copperinterconnection) and the copper film CF included in the plug PLG1A(first copper plug) are integrally provided, while the copper film CFincluded in the narrow interconnection NL2 (second copperinterconnection) and the copper film CF included in the plug PLG1B(second copper plug) are integrally provided.

Subsequent steps are repeatedly performed in substantially the same wayas the above-described steps, and duplicated description is omitted. Inthis way, the semiconductor device of this embodiment can bemanufactured.

<Characteristics in Manufacturing of Embodiment>

The semiconductor device of this embodiment is manufactured using themethod including the first characteristic point and the secondcharacteristic point in manufacturing. This allows the plug resistance(resistance value) of the plug PLG1A to be lower than the plugresistance (resistance value) of the plug PLG1B. Specifically, theresistivity of the tantalum film TF provided on the bottom of the plugPLG1A is lower than the resistivity of the tantalum film TF provided onthe bottom of the plug PLG1B. In detail, in this embodiment, thetantalum film TF provided on the bottom of the plug PLG1A has a crystalstructure of the α-Ta structure having low resistivity, while thetantalum film TF provided on the bottom of the plug PLG1B has a crystalstructure of the β-Ta structure having low resistivity. Hence, accordingto the manufacturing method of this embodiment, for example, it ispossible to suppress increase in plug resistance of the plug PLG1A to becoupled to the wide interconnection WL2 used as a power line, leading toimprovement in performance of the semiconductor device.

In addition, according to the method of manufacturing the semiconductordevice of this embodiment, it is possible to decrease the thickness ofthe barrier conductor film BCF provided on the inner wall of theinterconnection trench WD2B; hence, it is possible to improve thefilling properties for forming the narrow interconnection NL2 with theprocessing accuracy of about minimum working size. Specifically, forexample, the following significant effect can be provided by using themethod of manufacturing the semiconductor device of this embodiment.That is, there is provided the semiconductor device having in the samelayer the wide interconnection WL2 used as a power line that allows highcurrent to pass therethrough and the narrow interconnection NL2 formedwith the processing accuracy of about minimum working size, in whichwhile the plug resistance of the plug PLG1A to be coupled to the wideinterconnection WL2 is decreased, the filling properties for forming thenarrow interconnection NL2 as a fine interconnection is improved.

The first characteristic point and the second characteristic point inmanufacturing are now described. For example, the first characteristicpoint and the second characteristic point in manufacturing of thisembodiment are achieved in the respective deposition steps of thetantalum nitride film and the tantalum film illustrated in FIGS. 12 and13. Specifically, the first characteristic point and the secondcharacteristic point in manufacturing of this embodiment are achieved inthe step of forming the barrier conductor film BCF comprised of thetantalum nitride film TNF and the tantalum film TF over a region on theinterlayer insulating film IL2, the region including each of the innerwalls of the interconnection trench WD2A and the connection hole CNT1Aand each of the inner walls of the interconnection trench WD2B and theconnection hole CNT1B. Such steps are each a deposition step by asputtering process, and the first characteristic point and the secondcharacteristic point in manufacturing each relates to a depositioncondition in the sputtering process.

Here, description is made on a configuration and brief depositionoperation of a sputtering apparatus for performing the deposition stepsin the sputtering process.

FIG. 16 is a diagram illustrating a configuration of a sputteringapparatus used in this embodiment. In FIG. 16, the sputtering apparatushas a processing chamber CB in which a stage ST is arranged, and thesemiconductor substrate 1S is placed on the stage ST. In detail, anundepicted electrostatic chuck is provided in the stage ST so as to holdthe semiconductor substrate 1S. An undepicted center tap is provided inthe center of the electrostatic chuck. The center tap is configured tobe directly in contact with the semiconductor substrate. The center tapis electrically coupled to a bias supply BPS by which a substrate drawbias is applied to the semiconductor substrate 1S.

In the processing chamber CB, a target TAG comprised of a depositionmaterial is arranged at a position opposed to the semiconductorsubstrate 1S placed on the stage. The target TAG is electrically coupledto a DC power supply DCPS provided outside the processing chamber CB. Inthis configuration, power (target DC power) is supplied from the DCpower supply DCPS to the target TAG. The inside of the processingchamber CB is to be filled with argon gas (Ar gas) introduced therein.

The sputtering apparatus used in this embodiment is configured asdescribed above, and the deposition operation thereof is brieflydescribed below. In FIG. 16, first, the semiconductor substrate 1S isarranged on the stage ST arranged in the processing chamber CB.Subsequently, argon gas (Ar gas) is introduced into the processingchamber CB, the target DC power is supplied from the DC power supplyDCPS to the target TAG, and the substrate draw bias is applied from thebias supply BPS to the semiconductor substrate 1S. Plasma discharge thenstarts by a high electric field applied between the semiconductorsubstrate 1S and the target TAG. Consequently, the argon gas introducedinto the processing chamber CB is ionized, and the high-energy argon ionaccelerated by the high electric field collides with the target TAG. Asa result, target atoms are emitted from the target TAG as a reaction ofthe collision of the argon ion to the target TAG, and the emitted targetatoms adhere onto the semiconductor substrate 1S. This results in filmformation on the semiconductor substrate 1S. This is the end of thedeposition processing by the sputtering apparatus.

Specifically, in the method of manufacturing the semiconductor device ofthis embodiment, as illustrated in FIG. 12, the tantalum nitride filmTNF is formed over a region on the interlayer insulating film IL2, theregion including each of the inner walls of the interconnection trenchWD2A and the connection hole CNT1A and each of the inner walls of theinterconnection trench WD2B and the connection hole CNT1B by thesputtering process using the above-described sputtering apparatus. Thedeposition step of the tantalum nitride film is performed by thesputtering process with tantalum as the target TAG and with nitrogen gasintroduced into the processing chamber CB. The first characteristicpoint in manufacturing of this embodiment is given in the depositioncondition in this step.

FIG. 17 is a table showing the deposition condition in the depositionstep of the tantalum nitride film. In FIG. 17, an existing condition inthe deposition step of the tantalum nitride film is as follows: targetDC power is 20 kW, power of substrate draw bias is 650 W, and depositiontime is 4.6 sec. In contrast, the condition of this embodiment in thedeposition step of the tantalum nitride film is as follows: target DCpower is 20 kW, power of substrate draw bias is 650 W, and depositiontime is 6.9 sec. This shows that the first characteristic point inmanufacturing of this embodiment is in that the deposition time isincreased from 4.6 sec to 6.9 sec. In other words, the firstcharacteristic point in manufacturing of this embodiment is in that thedeposition time is increased to increase the thickness of the tantalumnitride film. Specifically, in this embodiment, the deposition time isincreased such that the thickness of the tantalum nitride film TNFprovided on the bottom of the connection hole CNT 1A illustrated in FIG.12 is within a range from 5 to 10 nm. Specifically, in the case of thedeposition time in the existing condition, the tantalum nitride film TNFprovided on the bottom of the connection hole CNT1A has a thickness ofless than 5 nm, and thereby the tantalum film TF provided on thetantalum nitride film TNF has a crystal structure of the β-Ta structurehaving high resistivity. In contrast, in the deposition condition ofthis embodiment, the deposition time is increased compared with theexisting condition; hence, the tantalum nitride film TNF provided on thebottom of the connection hole CNT1A has a thickness of 5 to 10 nm.Consequently, according to this embodiment, the tantalum film TFprovided on the tantalum nitride film TNF is allowed to have a crystalstructure of the α-Ta structure. That is, in the case where the tantalumnitride film TNF provided on the bottom of the connection hole CNT1A hasa thickness of 5 to 10 nm, the tantalum film TF provided on the tantalumnitride film TNF has a crystal structure of the α-Ta structure dependingon the crystal structure of the tantalum nitride film TNF.

Increasing the deposition time in the deposition step of the tantalumnitride film TNF means that the thickness of the tantalum nitride filmTNF provided on the bottom of the connection hole CNT1A is larger thanthat in the existing condition, and the thickness of the tantalumnitride film TNF provided on the bottom of the connection hole CNT1B isalso increased. In this case, although the filling properties forforming the narrow interconnection NL2 are likely to be degraded, thethickness of the tantalum nitride film TNF provided on the bottom of theconnection hole CNT1B is 3 nm or less even in the deposition conditionof this embodiment; hence, influence on the filling properties forforming the narrow interconnection NL2 is likely to be small.

In this regard, it is intended to improve the filling properties forforming the narrow interconnection NL2. From such a viewpoint, forexample, it is successful that while the deposition time in thedeposition step of the tantalum nitride film TNF is successfullyincreased, the deposition time in the deposition step of the tantalumfilm TF provided on the tantalum nitride film TNF is decreased. That is,when the thickness of the tantalum film TF is decreased incorrespondence to increase in thickness of the tantalum nitride filmTNF, the thickness of the barrier conductor film BCF as the totalthickness of the tantalum nitride film TNF and the tantalum film TF isnot changed; hence, it is possible to suppress degradation in fillingproperties for forming the narrow interconnection NL2. Specifically, forexample, when the tantalum nitride film TNF is formed to have athickness larger by 1 nm, the deposition time in the deposition step ofthe tantalum film TF should be decreased such that the thickness of thetantalum film TF is decreased by 1 nm. In this case, the thickness ofthe tantalum film TF formed on the tantalum nitride film TNF isdecreased not only on the bottom of the connection hole CNT1B and theinner wall of the interconnection trench WD2B, but also on the bottom ofthe connection hole CNT1A. Thus, the tantalum film TF has a crystalstructure of the α-Ta structure having low resistivity. In addition, thethickness itself of the tantalum film TF is decreased. These two eventssynergistically decrease the plug resistance of the plug PLG1A to becoupled to the wide interconnection WL2. Specifically, it is intended toachieve, at a high level, both decrease in plug resistance of the plugPLG1A to be coupled to the wide interconnection WL2 and improvement infilling properties for forming the narrow interconnection NL2 as a fineinterconnection. From such a viewpoint, it is desirable to increase thedeposition time in the deposition step of the tantalum nitride film TNF,but decrease the deposition time in the deposition step of the tantalumfilm TF provided on the tantalum nitride film TNF.

In the method of manufacturing the semiconductor device of thisembodiment, as illustrated in FIG. 13, the tantalum film TF is formed onthe tantalum nitride film TNF by the sputtering process using theabove-described sputtering apparatus, for example. The deposition stepof the tantalum film is performed in such a manner that nitrogen gas isfirst exhausted, and then the tantalum film is formed by the sputteringprocess with tantalum as a target and with a substrate draw bias beingapplied to the semiconductor substrate. The second characteristic pointin manufacturing of this embodiment is given in the deposition conditionin this step.

FIG. 18 is a table showing the deposition condition in the depositionstep of the tantalum film. In FIG. 18, an existing condition in thedeposition step of the tantalum film is as follows: target DC power is20 kW, power of substrate draw bias is 250 W, and electric potential ofthe semiconductor substrate is −255 V. In contrast, the condition ofthis embodiment in the deposition step of the tantalum film is asfollows: target DC power is 20 kW, power of substrate draw bias is 400W, and electric potential of the semiconductor substrate 1S is −350 V.This shows that the second characteristic point in manufacturing of thisembodiment is in that the electric potential of the semiconductorsubstrate 1S is varied from −255 V to −350 V. In other words, the secondcharacteristic point in manufacturing of this embodiment is in that theabsolute value of the electric potential of the semiconductor substrate1S is increased compared with that in the existing condition.Consequently, according to this embodiment, the tantalum film TFprovided on the tantalum nitride film TNF is allowed to easily have acrystal structure of the α-Ta structure. For example, increasing theabsolute value of the electric potential of the semiconductor substrate1S means that tantalum atoms emitted from the target TAG are acceleratedand adhere onto the tantalum nitride film TNF. In this case, since thetantalum atoms each have a large kinetic energy, even after the tantalumatoms adhere onto the tantalum nitride film TNF, each tantalum atomeasily moves so as to reflect the crystal structure of the tantalumnitride film. As a result, according to this embodiment, the tantalumfilm TF provided on the tantalum nitride film TNF easily has a crystalstructure of the α-Ta structure having low resistivity.

Thus, it is intended to make the tantalum film TF provided on thetantalum nitride film TNF to have a crystal structure of the α-Tastructure having low resistivity. From such a viewpoint, it is desirableto increase the absolute value of the electric potential of thesemiconductor substrate 1S. For example, it is desirable to apply asubstrate draw bias such that the electric potential of thesemiconductor substrate 1S is within a range from −350 V to −800 V. Forexample, such a condition can be given by applying the substrate drawbias to the semiconductor substrate 1S at a power of 400 to 1000 W. Theelectric potential of the semiconductor substrate 1S is thus adjusted tobe within the range from −350 V to −800 V by applying the substrate drawbias at a certain power. The power however is considered to varydepending on types of the sputtering apparatus. In any type ofsputtering apparatus, therefore, power for applying the substrate drawbias should be supplied such that the electric potential of thesemiconductor substrate 1S is finally within a range from −350 V to −800V.

Consequently, according to the method of manufacturing the semiconductordevice of this embodiment, a synergetic effect of the first and secondcharacteristic points in manufacturing is provided, and thereby it ispossible to achieve both decrease in plug resistance of the plug PLG1Ato be coupled to the wide interconnection WL2, and improvement infilling properties for forming the narrow interconnection NL2 as a fineinterconnection. It is thus intended to achieve both decrease in plugresistance of the plug PLG1A to be coupled to the wide interconnectionWL2, and improvement in filling properties for forming the narrowinterconnection NL2 as a fine interconnection. From such a viewpoint, itis desirable to combine the first characteristic point in manufacturingwith the second characteristic point in manufacturing. This however isnot limitative. For example, it is acceptable to use a configurationwhere only the first characteristic point in manufacturing is performedor a configuration where only the second characteristic point inmanufacturing is performed. Specifically, the first characteristic pointin manufacturing relates to the deposition step of the tantalum nitridefilm, while the second characteristic point in manufacturing relates tothe deposition step of the tantalum film; hence, the first and secondcharacteristic points can be performed independently of each other.

<Modification>

A modification of this embodiment is now described. This modification isbased on the following technical idea. That is, in the deposition stepof the tantalum nitride film TNF illustrated in FIG. 12, introductiontiming of nitrogen gas to be introduced into the processing chamber CBof the sputtering apparatus is advanced compared with that in theexisting technique.

FIG. 19 is a diagram for explaining introduction timing of nitrogen gasin the deposition step of the tantalum nitride film TNF in thismodification. In FIG. 19, in the sputtering apparatus, an ignition stepof starting plasma discharge of argon gas is first performed, and thenthe deposition step (TaN deposition step) of the tantalum nitride filmTNF is performed, and then the deposition step (Ta deposition step) ofthe tantalum film TF is sequentially performed. At this time, asillustrated in FIG. 19, target DC power is stepwise increased in theignition step, and therethrough plasma discharge is started. The targetDC power is then maintained to a fixed value over the TaN depositionstep and the Ta deposition step. In an existing technique in FIG. 19,nitrogen gas is introduced after the ignition step is finished.Actually, sputtering occurs in the process of stepwise increasing thetarget DC power in the ignition step. Hence, in the existing technique,the tantalum film is formed in the stage of the ignition step, andformation of the tantalum nitride film begins upon introduction ofnitrogen gas in the subsequent TaN deposition step. In contrast, in thismodification, as illustrated in FIG. 19, nitrogen gas is introduced intothe processing chamber CB in a stage of starting the ignition step (astep before the TaN deposition step). Consequently, according to thismodification, the tantalum nitride film can be formed over the ignitionstep to the TaN deposition step. That is, in this modification, sincenitrogen gas is introduced into the processing chamber CB in the stageof starting the ignition step, the tantalum nitride film can also beformed in the stage of the ignition step. As a result, according to thismodification, even if deposition time in the TaN deposition step is notincreased, deposition time of the tantalum nitride film TNF can besubstantially increased, and thereby the first characteristic point inmanufacturing can be provided. Hence, according to this modification,the tantalum nitride film TNF provided on the bottom of the connectionhole CNT 1A is allowed to have a thickness of 5 to 10 nm withoutreducing throughput of the sputtering apparatus. Consequently, accordingto this modification, the tantalum film TF provided on the tantalumnitride film TNF is allowed to have a crystal structure of the α-Tastructure.

<Effects of Embodiment>

According to this embodiment (including the modification), for example,the following effects can be provided.

(1) According to this embodiment, for example, the following significanteffect can be provided. That is, there is provided the semiconductordevice having in the same layer the wide interconnection WL2 used as apower line that allows high current to pass therethrough and the narrowinterconnection NL2 formed with the processing accuracy of about minimumworking size, in which while the plug resistance of the plug PLG1A to becoupled to the wide interconnection WL2 is decreased, the fillingproperties for forming the narrow interconnection NL2 as a fineinterconnection is improved.

(2) According to this embodiment, for example, the respective tantalumnitride films TNF having different thicknesses can be formed in onesputtering step on the respective bottoms of the plugs (PLG1A and PLG1B)to be coupled to the wide interconnection WL2 and the narrowinterconnection NL2 that have different line widths and are provided inthe same interconnection layer. According to this embodiment, therefore,the tantalum nitride film provided on the bottom of the plug PLG1A to becoupled to the wide interconnection WL2 and the tantalum nitride filmprovided on the bottom of the plug PLG1B to be coupled to the narrowinterconnection NL2 are not necessary to be formed in separatesputtering steps; hence, the sputtering process for forming the tantalumnitride films having different thicknesses can be simplified, andthereby manufacturing cost of the semiconductor device can be reduced.

Although the invention achieved by the inventors has been described indetail according to one embodiment thereof hereinbefore, the inventionshould not be limited thereto, and it will be appreciated that variousmodifications or alterations thereof may be made within the scopewithout departing from the spirit of the invention.

What is claimed is:
 1. A semiconductor device, comprising: (a) a firstcopper interconnection and a second copper interconnection provided inthe same layer; (b) a first copper plug arranged in an underlayer of thefirst copper interconnection and coupled to the first copperinterconnection; (c) a second copper plug arranged in an underlayer ofthe second copper interconnection and coupled to the second copperinterconnection; (d) a first barrier conductor film contained in thefirst copper plug; and (e) a second barrier conductor film contained inthe second copper plug, the first copper interconnection having a linewidth larger than a line width of the second copper interconnection, thefirst copper plug and the second copper plug having the same size andprovided in the same layer, each of the first barrier conductor film andthe second barrier conductor film being comprised of a tantalum nitridefilm and a tantalum film provided over the tantalum nitride film,wherein a resistance value of the first copper plug is lower than aresistance value of the second copper plug, and wherein first thicknessof the tantalum nitride film provided on a bottom of the first copperplug is larger than second thickness of the tantalum nitride filmprovided on a bottom of the second copper plug.
 2. The semiconductordevice according to claim 1, wherein the first thickness is 5 nm or moreand 10 nm or less.
 3. The semiconductor device according to claim 1,wherein the second thickness is more than 0 nm and 3 nm or less.
 4. Thesemiconductor device according to claim 1, wherein resistivity of thetantalum film provided on the bottom of the first copper plug is lowerthan resistivity of the tantalum film provided on the bottom of thesecond copper plug.
 5. The semiconductor device according to claim 4,wherein the tantalum film provided on the bottom of the first copperplug has a crystal structure of a α-Ta structure, and the tantalum filmprovided on the bottom of the second copper plug has a crystal structureof a β-Ta structure.
 6. The semiconductor device according to claim 1,wherein the first copper interconnection is a power line configured topower supply potential.
 7. The semiconductor device according to claim1, wherein a copper film included in the first copper interconnectionand a copper film included in the first copper plug are integrallyprovided, and a copper film included in the second copperinterconnection and a copper film included in the second copper plug areintegrally provided.
 8. A semiconductor device, comprising: (a) a firstcopper interconnection and a second copper interconnection provided inthe same layer; (b) a first copper plug arranged in an underlayer of thefirst copper interconnection and coupled to the first copperinterconnection; (c) a second copper plug arranged in an underlayer ofthe second copper interconnection and coupled to the second copperinterconnection; (d) a first barrier conductor film contained in thefirst copper plug; and (e) a second barrier conductor film contained inthe second copper plug, the first copper interconnection having a linewidth larger than a line width of the second copper interconnection, thefirst copper plug and the second copper plug having the same size andprovided in the same layer, each of the first barrier conductor film andthe second barrier conductor film being comprised of a tantalum nitridefilm and a tantalum film provided over the tantalum nitride film,wherein a resistance value of the first copper plug is lower than aresistance value of the second copper plug, and wherein resistivity ofthe tantalum film provided on a bottom of the first copper plug is lowerthan resistivity of the tantalum film provided on a bottom of the secondcopper plug.
 9. The semiconductor device according to claim 8, whereinthe tantalum film provided on the bottom of the first copper plug has acrystal structure of a α-Ta structure, and the tantalum film provided onthe bottom of the second copper plug has a crystal structure of a β-Tastructure.
 10. The semiconductor device according to claim 8, whereinthe first copper interconnection is a power line configured to powersupply potential.
 11. The semiconductor device according to claim 8,wherein a copper film included in the first copper interconnection and acopper film included in the first copper plug are integrally provided,and a copper film included in the second copper interconnection and acopper film included in the second copper plug are integrally provided.